1. The main program file exercise_test.py (similar to alien project's alien_investment. Py)

import sys
import pygame
from pygame.sprite import Group
import game_functions as gf
from settings import Settings
from rocket import Rocket


def run_game():
	
	#Initialize background settings
	pygame.init()
	#Create a display window called screen
	ai_settings = Settings()
	screen = pygame.display.set_mode((ai_settings.screen_width,
		ai_settings.screen_height))
	
	pygame.display.set_caption("Blue Sky")
	
	#Create a rocket
	rocket = Rocket(ai_settings, screen)
	
	#Create a group to store bullets
	bullets = Group()
	while True:
		gf.check_events(ai_settings, screen, rocket, bullets)
		rocket.update()
		gf.update_bullets(bullets, ai_settings)

		gf.update_screen(ai_settings, screen, rocket, bullets)
		

run_game()

2,game_function.py

import sys
import pygame
from bullet import Bullet

def check_keydown_events(event, ai_settings, screen, rocket, bullets):
	"""Response button"""
	if event.key == pygame.K_RIGHT:
		rocket.moving_right = True
	elif event.key == pygame.K_LEFT:
		rocket.moving_left = True
	elif event.key == pygame.K_UP:
		rocket.moving_up = True
	elif event.key == pygame.K_DOWN:
		rocket.moving_down = True
	elif event.key == pygame.K_SPACE:
		#Create a bullet and add it to the group bullets
		if len(bullets) < ai_settings.bullets_allowed:
			new_bullet = Bullet(ai_settings, screen, rocket)
			bullets.add(new_bullet)
		
def check_keyup_events(event, rocket):
	"""Response loosening"""
	if event.key == pygame.K_RIGHT:
		rocket.moving_right = False
	elif event.key == pygame.K_LEFT:
		rocket.moving_left = False
	elif event.key == pygame.K_UP:
		rocket.moving_up = False
	elif event.key == pygame.K_DOWN:
		rocket.moving_down = False

def check_events(ai_settings, screen, rocket, bullets):
	"""Respond to cases and mouse events"""
	for event in pygame.event.get():
		if event.type == pygame.QUIT:
			sys.exit()
		elif event.type == pygame.KEYDOWN:
			check_keydown_events(event, ai_settings,screen, 
				rocket, bullets)
				
		elif event.type == pygame.KEYUP:
			check_keyup_events(event, rocket)
				
def update_screen(ai_settings, screen, rocket, bullets):
	"""Update the image on the screen and switch to the new screen"""
	#Redraw the screen every time you cycle
	screen.fill(ai_settings.bg_color)
	#Redraw all bullets behind rockets and aliens
	for bullet in bullets.sprites():
		bullet.draw_bullet()
	rocket.blitme()
		
	#Make the most recently drawn screen visible
	pygame.display.flip()

def update_bullets(bullets, ai_settings):
	"""Update the location of bullets and delete the disappeared bullets"""
	bullets.update()
	#Delete the disappeared bullets. Use the right border of the bullets to set it not to exceed the screen width
	for bullet in bullets.copy():
		if bullet.rect.right >= ai_settings.screen_width:
			bullets.remove(bullet)
	#Success can be detected by the following code
	"""print(len(bullets))"""

3,rocket.py

import pygame

class Rocket():
	def __init__(self, ai_settings, screen):
		#Initialize the rocket and set its initial position
		self.screen = screen
		self.ai_settings = ai_settings
		#Loading rocket image and obtaining its external rectangle
		self.image = pygame.image.load('images/rocket.bmp')
		self.rect = self.image.get_rect()
		self.screen_rect = screen.get_rect()
		
		#Put each rocket in the center of the screen
		self.rect.centerx = self.screen_rect.centerx
		self.rect.centery = self.screen_rect.centery
		
		#Store small values in the spaceship's attribute center
		self.center = float(self.rect.centerx)
		self.center_up_down = float(self.rect.centery)

		#Mobile logo
		self.moving_right = False
		self.moving_left = False
		self.moving_up = False
		self.moving_down = False
	def update(self):
		"""Adjust the position of the rocket according to the moving sign,Right left upper and lower"""
		if self.moving_right and self.rect.right < self.screen_rect.right:
			self.center += self.ai_settings.rocket_speed_factor
		if self.moving_left and self.rect.left > 0:
			self.center -= self.ai_settings.rocket_speed_factor
		if self.moving_up and self.rect.top > 0:
			self.center_up_down -= self.ai_settings.rocket_speed_factor
		if self.moving_down and self.rect.bottom < self.screen_rect.bottom:
			self.center_up_down += self.ai_settings.rocket_speed_factor
			
		#Update rect object according to self.center
		self.rect.centerx = self.center
		self.rect.centery = self.center_up_down

	def blitme(self):
		"""Draw the rocket at the specified position"""
		self.screen.blit(self.image, self.rect)

4,setting.py

class Settings():
	"""Create a class with all settings"""
	
	def __init__(self):
		self.screen_width = 800
		self.screen_height = 600
		self.bg_color = (0, 191, 255)
		
		#Set the speed of the ship
		self.rocket_speed_factor = 1.5
		#Bullet setting
		self.bullet_speed_factor = 1
		self.bullet_width = 15
		self.bullet_height = 3
		self.bullet_color = 60, 60, 60
		self.bullets_allowed = 3

5,bullet.py

import pygame
from pygame.sprite import Sprite

class Bullet(Sprite):
	"""A class that manages the bullets fired by a spaceship"""
	
	def __init__(self, ai_settings, screen, rocket):
		"""Create a bullet object at the ship's location"""
		super().__init__()
		self.screen = screen
		
		#Create a rectangle representing the bullet at (0, 0) and set the correct position
		self.rect = pygame.Rect(0, 0, ai_settings.bullet_width, ai_settings.bullet_height)
		self.rect.centerx = rocket.rect.centerx
		self.rect.centery = rocket.rect.centery
		
		#Stores the bullet position as a decimal point
		self.y = float(self.rect.y)
		self.x = float(self.rect.x)
		
		self.color = ai_settings.bullet_color
		self.speed_factor = ai_settings.bullet_speed_factor
		
	def update(self):
		"""Moving bullets to"""
		#Update the small value indicating the bullet position, and determine the direction of the bullet by changing x and y
		self.x += self.speed_factor
		#Update the location of the rect that represents the bullet
		self.rect.x = self.x
			
	def draw_bullet(self):
		"""Draw bullets on the screen"""
		pygame.draw.rect(self.screen, self.color, self.rect)